Pebble heater apparatus and method for heat exchange



Feb- 19, 1952 c. ALEXANDER ETA. 2,585,984 'u PEBBLE HEATER APPARATUS ANDMETHOD FOR HEAT EXCHANGE Filed May 2, 1946 CRUZ-AN ALEXANDER HARRIS A.DUTCHER lex/WW2? M ATTORNEYS Patented Feb. 19, 1952 assassi PEBBLEHEATERAPPAATUS AND METHOD FOR HEAT EXCHANGE Cruzan Alexander and HarrisA. Dutcher, Bartlesville, Okla., assignors to Phillips PetroleumCompany, a corporation `oi. Delaware Application May 2, 194'6, serialNo. 666,767

19 Claims.

This invention relates to the treatment of uids. In one particularaspect this invention relates to pebble heaters for the heating of gasesto hightemperatures. In still another aspect this invention relates to amethod and apparatus for heating hydrocarbons t rel-atively hightemperatures for conversion thereof to other hydrocarbons andhydrogen-containing gases. Another aspect of this invention relates to areaction chamber and a method for heating the same.

In hydrocarbon conversion processes which require high temperature andwhich are endothermic in character, such as thermal cracking and thermaldehydrogenation of hydrocarbons, pebble heater type apparatus functionsmost satisfactorily. Also in the superheating of gases, such as steam,pebble heaters may also be applicable. The pebble heater methods entailthe heating of refractory pebbles in a heating chamber by the combustionof fuels and the transference of resulting- `hydrocarbons to producelighter products, the

pebbles leaving the cracking chamber are still at a very hightemperature and can be handled in mechanical conveyor equipment only ifhigh temperature alloy materials are used. Furthermore, in conventionalapparatus it is difcult if not impossible to obtain the hightemperatures that are so advantageous in cracking of the lighterhydrocarbons wherein temperatures of 1500 to 2000 F. or higher are oftennecessary. Consequently, it is highly desirable to provide a pebbleheating type apparatus and reaction chamber i which requires fewmechanical moving parts.

An object of the present invention is to provide ame'thod and apparatusfor the attainment of extremely high temperatures in a pebble heatertype furnace.

i Another object is toprovide a novel apparatus for supplying heat to orremoving heat from gases.

Still another object of the present invention vis t0 provide anapparatus for heating and reacting materials in a single unitaryapparatus.

7 ing the characteristics of the conventional pebble heater type furnacewithout the necessity of mechanical conveyors for conveying the pebbles.

It is a further object to provide a method and apparatus for heatinggases with pebbles whereby large temperature changes of the pebbles areminimized.

Various other objects and advantages will become apparent to thoseskilled in the art from the accompanying description and disclosure.

For a full understanding of the nature and objects of invention,reference should be had to the following detailed description taken inconnection with the accompanying drawing.

In the drawing- Figure l is an elevational view, partially in crosssection, diagrammatically illustrating apparatus for heating a. uidaccording to the present invention.

Figure 2 is another modification of the present invention also shown inan elevational View, partially in cross section, illustrating apparatusfor heating a fluid.

In Figure 1, which diagrammatically illustrates one arrangement ofapparatus for this invention, numeral 8 designates an elongated,enclosed,

vhollow body which contains both a combustion Y zone and a heating orreaction zone. The hollow body is divided into a reaction zone 23, anintermediate zone and a combustion zone 'l by septa i8 and Il,respectively. The form of the hollow body is preferably cylindrical as amatter of convenience in both construction and operation, but hollowbody 8 may be of any other particular form as desired. Hollow body 8 canbe constructed of various types of metals, such as steel, nickel andchrome alloy steels, or Inconel. and,

preferably, is lined or covered both on the inside and the outsidethereof by suitable materials (not shown). 'Ihe lining on the inside ofcylinder 8 will usually comprise refractory material, such as thosematerials which are resistant to high temperatures and to spelling bythe pebbles. Suitable materials for such purposes, for example, arekaolin, alumina-diaspore, sillimanite, bonded silicon carbide, bondedfused alumina, etc. The covering on the outside of cylinder 8 is usuallyasbestos, or the like, for preventing the loss of heat from cylinder 8.Under some circumstances cylinder 8` is constructed entirely of ceramicrefractory material and may be constructed in sections, each l sectionof the same or different material, with- 3 of this invention, septum I8is perforated and contains a vent or lumen, preferably in the centerthereof, as shown by numeral I9. Septum I8 may be constructed of anytype of material which is resistant to high temperatures and which hassuilcient strength to support its own weight and the weight of a layerof pebbles on the top thereof f In some instances septum I 3 is made ofa metal, such as a high alloy metal as Inconel; in other instances it isconstructed of suitable ceramic or porcelain material. Usually theconstruction of septum I8 is of'a metal and is in the form of aperforated disc or plate, or a wire screen, so that pebbles collect onthe top thereof in a layer and flow through the holes or perforationstherein into chamber 25 below. Septum Il may be constructed of materialssimilar to those described with respect to th'e construction of septumI8. The form of septum I I, however, is somewhat different, preferably,in the form of a funnel-shaped member having a vent or opening,generally in the center thereof, for passage of uid therethrough. SeptumII may also be of a relatively greater thickness (as shown) than septumIl! and capable of supporting a relatively deep layer of pebbles on thetop thereof. When septum I8 is of such a relatively massiveconstruction, it will be made of ceramic material. When septum II isconstructed more or less as a thin plate or sheet in the form of afunnel or cone, it will be made of metal.

Element I3 is an elongated conduit open at both ends and is positionedconcentrically to vent I of septum II. The lower end of conduit I3terminates adjacent and above vent I6. The length of conduit,preferably, constitutes only a minor proportion of the length of theintermediate chamber and serves as a passageway for the flow of gasesand pebbles from chamber 25 to reaction chamber 23. In other words, thelength of conduit I3 is usually less than about one-half the length ofchamber 25. Conduit I3 is supported at the proper location in chamber 25by suitable rods or beams I4. Conduit I3 is constructed of a suitablematerial, such as porcelain, In-conel, or the like. Element I2 providesa restricted area in the lower end of conduit I3 and operates as anozzle. Fuel and air are introduced through conduits 4 and 5 intocombustion chamber 'I in which combustion of the fuel and air is eected.The combustion products or flue gases pass from combustion chamber 'Ithrough vent I5, conduit I3 into intermediate chamber 25. Flue gases areremoved from intermediate chamber 25 through conduits 24. The uid to betreated or heated is passed into the lower portion of zone 23 throughconduits 26 and the resulting eflluent is removed from the top of zone23 through conduit 28 and valve 29. Element 21 is a shield or like meansfor deecting pebbles and preventing their passage from chamber 23through conduit 28.

Valve 29 is a conventional motor or automatic control valve which isactuated by transmission means 3l electrically or pneumaticallyresponsive to the pressure in intermediate chamber 25. For the varioustypes of hook-ups of an automatic valve and its operation reference ismade to the adequate description in Industrial Instruments forMeasurement and Control, Rhodes, T. J., McGraw-Hill Book Company, 1941.

Septum or screen I8 is perforated with the appropriate number and sizeof holes to maintain a desired depth of pebbles, shown at 2|, on theseptum and at the same time to permit pebblesv to fall through theperforations. Conduit I3 is located close to septum II so that pebblesaccumulate on the top of septum II, as indicated by numeral 22, andsimultaneously continuously oW through the annular space between septumII and the lower end of conduit I3 into the gas stream from vent I6.

Various modifications, alterations of the elements of Figure 1 may bepracticed without departing from the scope of this invention. As shown,feed entering through conduits 25 is introduced in tangential direction;however, the feed may be introduced without a tangential direction ifdesired. Furthermore, flue gases being removed through conduits 24 maybe removed in a tangential direction if desired. Vent or lumen I9 may beconstructed in any form and may extend further into reaction zone 23than shown. In some instances it may be desired and preferable toeliminate combustion zone 'I and in so doing the combustion gases andair are introduced directly through vent I6 and are burned in conduitI3. Combustion zone 1 may be a separate unit from cylinder B and theeffluent from zone 'I is passed to inlet or vent I6 through suitableconduits (not shown). A screen or the like (not shown) may be placedover the top of vent I6 in order to prevent pebbles falling from zone orchamber 25 to combustion zone 1. Nozzle or restriction I2 may also beomitted if desired and conduit I3 may comprise a bundle or group ofsmall conduits (not shown) which together comprise conduit I3.

A heat exchanger (not shown) may be provided for heat exchange of theflue gases in conduits 24 with incoming feed in conduits 26 or with airin conduits 5.

In Figure 2, which diagrammatically shows another modication ofapparatus for practicing the present invention, element 53 as in Figure1 is an elongated, enclosed, hollow body, preferably of a cylindricalshape. Cylinder 53 is separated into an upper chamber l2, a reactionchamber 'II and a combustion chamber 5l' by a perforated septum 68 and afunnel-shaped septum 59, respectively. The construction and materialsare similar to those of the apparatus described in Figure 1, and,therefore, such description is unnecessary with regard to Figure 2. Asin Figure l septum 68 may comprise a wire screen or the like for thecollection of pebbles thereon.

A conduit 62 is passed through screen or septum 68 in open communicationbetween chamber l2 and the lower portion of reaction chamber 'Il asshown. Conduit 62 is held in position in reaction zone 'II by means ofsupporting rods 66. Conduit 62 is preferably an elongated cylindricalpipe or tube and is positioned so that it protrudes through the centerof septum 68 and extends substantially the entire length of chamber 'IIand terminates adjacent a vent 58 of septum 59. Vent 58 is preferablylocated in the center of septum 59. Fuel and air are introduced intocombustion zone 5l through conduits 54 and 56, respectively. Theproducts of combustion are passed from comvbustion zone 51 to zone 72through conduit 62 and are removed therefrom through a conduit 14.Conduit 'I6 is a uid inlet for introduction of feed into the upperportion of reaction zone 'I I. Withdrawal of an effluent from zone 'Ilis eected through conduit T8. The lower portion of conduit 62 may berestricted in cross sectional area by element 8|. Element 'I3 comprisesa guard or shield for preventing the passage of pebbles from chamber l2ythrough conduit 14 which removes -hot gases. M Vthrough orifice or ventI6 is substantially in exthe heating uid from chamber 12. Numerals 63and 69 indicate the accumulation of pebbles in the lower portion ofreaction chamber 'II and chamber 12, respectively.

As described 4in Figure 1, various alterations and modifications may beeffected in the apparatus shown in Figure 2 without departing from thescope of this invention. Preferably, conduit 'I8 is located in the lowerportion of reaction zone 'II below the accumulation of pebbles 63therein but alternatively it may be located above the accumulation ofpebbles 63. Fluid introduced into chamber 'II through conduit 'I6 passesthrough the accumulation of pebbles 63 and out of reaction zone 'IIthrough conduit 'I8. Conduit 62 ex- The term pebble as used throughoutthe specication denotes any refractory material, either ceramic ormetallic, in flowable form and size which can be utilized to carry heatfrom one zone to another. tially spherical and are from as large asabout 1 inch in diameter to as small as will pass through a 200 meshscreen. Th-e actual size of the pebbles Will of course depend uponcharacter of the refractory material, such as its density, and upon thegas velocity of the supporting fluid stream. In general, the pebblesmust be of refractory material which will withstand temper-atures ashigh as the highest temperatur-e attained in the pebble heating zone.Pebbles which will withstand temf peratures within the range of about3000 to 3500 F. are now in use and comprise highly heat resistantmaterial, such as fused alumina. The preferred size of the pebbles whenusing a ceramic refractory material is about that size which will:

pass through an 8 mesh screenand willberetained on a 60 mesh screen. Thepebbles themselves may comprise a ycatalytic material or may cornprisean inert material impregnated with a catalytic material for the processin which they are being used. Therefore, in many instances the pebbleswill comprise a metallic catalyst or will comprise a ceramic materialimpregnated with a metallic catalyst. I

Operation In the operation of Figure 1, a feed which may comprisehydrocarbon reactants or an inert gas to be superheated is continuouslyor intermittently passed into reaction zone 23 through conduit 26. Thefeed material in reaction zone 23 undergoes the desired treatment andachieves the desired temperature by contact with pebbles therein. Afterthe gas has remained in chamber 23 for sufiicient length of time toachieve the Iappropriate temperatureit is continuously or intermittentlyremoved therefrom through conduit 28 and valve 29.

In order to heat the pebbles to a suciently high temperature to transferheat to the gas in chamber 23, fuel and air 'enter combustion zone Ithrough 4conduits' 4 and 5, respectively, and are burned therein. Thefiue gas or combustion products from combustion zone 'l continuouslypass through an orifice or vent I6 into chamber 25 and pass upwardthrough conduit I3 at a high rate of speed as the result of theexpansion of the The rate 'of flow of gases 'passing cess of the flamepropagation of the combustion Pebbles are conventionally substan- :Y

` gases. Therefore according to one modification,

lrate of fiame propagation. In either of the above methods of operation,theA gases from the chamber 1 passing through conduit I3 achieve a veryhigh rate of speed in excess of about 10 to about 15 feet per second andoften as high as about 30 to about 40 feet per second, which speeddepends to a large extent upon the cross sectional area of the inside ofconduit I3. The high rate of speed of the gases passing from vent I6into conduit I3 through restricted area I2 aids in continuously forcingpebbles which have accumulated at 22 into the gaseous stream by aninspirating eiect. The pebbles falling into conduit I3 are heated andsuspended in the gaseous stream which throws them upward from the upperend of conduit I3 through vent IS and into upper chamber or reactionzone 23. When the pebbles comprise a catalytic material, the heating ofthe pebbles in conduit I3 also regenerates or reactivates the catalyticmaterial. Because of the sudden increase in cross sectional areaconfining the gases when they pass from conduit I3 into the open spaceof chamber 25, the Velocity of gaseous stream rapidly decreases. Fluegases are removed from chamber 25 through conduits 23. However, becauseof the inertia and momentum of the pebbles, the heated pebbles passupward through vent I9. In chamber 23 the pebbles lose their velocityand fall downward onto screen I8. Some of the pebbles may havesufficient velocity to impinge upon shelf 2'! which changes theirdirection and makes them drop onto screen I8. The size of theperforations in screen I8 with regard to the size of the pebbles and tothe rate at which they accumulate is such that a layer of pebbles 2|,often several inches in thickness, is continuously maintained on the topside of screen I8. The pebbles fall through screen I8 at substantiallythe same rate as they accumulate thereon. The layer of pebbles 2| onscreen I8 prevents or hinders the passage of gase's from reaction zone23 to chamber 25 or vice versa; thus the intermingling of gases fromeach chamber is prevented or minimized. As shown the feed entersreaction zone 23 is a tangential direction tc attain a tangential motionand by this motion the feed aids in spreading out the stream of pebblesflowing from chamber 25 into chamber 23 and ensures an even distributionof pebbles on screen I8.

Mechanical means for shaking screen I8 (not shown) may be used to aid inforcing the pebbles through the perforations in screen I8 and also bycontrolling the amountv of shaking the height of the pebbles on screen I8 can be adjusted.

The pebbles give up the heat acquired in conduit I3 and chamber 25 tothe incoming fluid feed in reaction chamber 23. After accumulation onscreen I 8 the, pebbles# continuously fall through the perforationstherein and drop by gravity into .the lower `portion of chamber 25 forreheating. l

-tum Il serves as a proport'ioning device for the flow' of pebbles fromchamber 25 into the high 'Ispeed gas stream from lvent I6. Y

11n-circumstances where it is objectionable or undesirable for any gasesfrom chamber 23 to pass into chamber 25, a higher pressure may bemaintained in chamber 25 than in chamber 23 by means of valve 29 andtransmission means 3| responsive to the prevailing pressure in chamber25. If a slightly excess pressure, e. g'. between about 2 and about 5pounds per square inch difference, is maintained in chamber 23, a smallamount of gases continuously flows from chamber 23v to chamber 25through vent I9 while at the same time pebbles are passing upward fromchamber 25 to chamber 23 through vent I9. The pebbles in chamber 23which are at a very high temperature, such as about 1500 to about 3000F.,

l give off much of their available heat before falling into lowerchamber 25 where they are reheated.

Since the operation in Figure 2 in most respects is similar to theoperation in Figure l, only a brief discussion of the operation ofapparatus illustrated in Figure 2 will be made. Figure 2 is anothermodification of the present invention showing apparatus for the heating(or cooling) of gases. A uid feed enters zone 1I of cylinder 53 throughconduit 15. This feed contacts falling pebbles in zone 1I and passesthrough the accumulation of pebbles 63 in the lower portion oi zone 1Iand thence from cylinder 53 through conduit 1li which may have a screen(not shown) over the mouth thereof to retain pebbles in zone 1 I. Itshould be noted that in the preferred method of operation shown, theaccumulation of pebbles G3 in zone 1I is such that the gases fromconduit s must pass through the accumulation of pebbles before being'removed from cylinder' 53. Fuel and air are passed into combustion zone51 through conduits 54 and 55, respectively, The combustion mixture isburned in zone 51 and thehot combustion products or ue gases arecontinuously passed from zone 51 through vent or orifice 58 intoelongated conduit 62 through restricted area 6I. Since the fluid iiowingthrough vent 5S and restricted area 6I into conduit 62 is at a highvelocity, pebbles fall into the liowing gaseous stream by an inspirationeffect as well as by their own weight and are heated and suspended inthe hot gaseous stream. In thisembodiment of the invention the gasesflow in conduit 52 only at a sucient rate to suspend the pebbles andconvey them along with the hot flue gases through conduit 62 to upperchamber 12. In upper chamber 12, becauseof the increased cross sectionalarea of that zone, the gases lose much of their velocity. The suspendedpebbles fall onto screen 58, as shown. Those pebbles which may haveenough velocity to pass to the upper portion of chamber 12 impingeagainst shield 13 and are deflected downward onto screen 68. Theaccumulation of pebbles on screen 63 indicated by numeral 59 preventsthe passage of gases from chamber 12 to chamber 1I, as described Withrespect to Figure 1.

Pebbles at a relatively high temperature, e. g. 1500 to 2500" F., dropthrough perforations in screen 58 and fall by gravit;7 through chamber1I to the lower portion thereof and'accumulate as indicated by 63. Inchamber 1I the pebbles give up the heat acquired in conduit 62 to thefeed entering through conduit 1G.

As in the case of Figure 1 combustion zone 51 may'comprise only a mixingzone and combustion may take place entirely in conduit 62 and upperchamber 12 without departing from the scope of this invention. Even insome instances zone 51 may be separate from cylinder 53 (or zone 1 fromcylinder is' of Figure 1) without departing from the scope of theinvention.

Aparticular novelty of the modification shown in Figure 1 lies in thefact that the pebbles from the heating zone 25 pass to reaction zone 23by their own inertia and momentum achieved by their suspension in thegaseous stream in conduit I3. On the other hand a particular novelty ofthe modification shown in Figure 2 lies in the fact that the pebblesaccumulating in reaction zone 'II are passed therefrom by beingsupported in a gaseous stream in conduit 62 throughout their passagefrom zone 1I to upper zone 12. For the operation of Figure l a highervelocity of gases must be maintained in conduit I3 than is usuallymaintained in conduit 62 of Figure 2, because in Figure 1 the pebblesare passed to the upper zone 23 by force of their inertia and momentumWhile in Figure 2 the pebbles are passed into upper zone i2 by asuspension or gas lift effect. Although Figure 2 comprises the preferredmodification of the present invention, in some instances it may be moredesirable and more practical to use the type of apparatus and methodshown in Figure I.

The feed entering cylinder 53 through conduit 15 of Figure 2 may beintroduced tangentially as in the case of Figure 1. Furthermore, thefeed of Figure 2 may be introduced through conduit 'I3 and the resultingproduct removed through conduit 15 without departing from the scope ofthis invention.

It is possible in some instances to operate zone 23 of Figure 1 as thecombustion zone for heating the pebbles and zone 25 and conduit I3 asthe reaction zone. Thus, the reactant gases are introduced into zone 25through inlet I6 and are removed therefrom through conduits 24. Air andfuel are introduced into zone 23 through lines 26 and a flue gas isremoved through line 28. The reactantgases themselves suspend thepebbles in conduit I3 according to this modification.

The present invention may be applied to exothermic reactions as well asendothermic reactions. For example, feed introduced through conduits 54and 5S in Figure 2 may undergo an exothermic reaction in chamber 51. Thereaction efiuent passes from zone 51 through conduit 62 at a rate suchthat cool pebbles are supported therein and absorb heat from thereaction effluent. The pebbles are then discharged from conduit 52 intozone 12 where they drop back into cooling zone -1I, as shown, but at asubstantially higher temperature than when introduced into conduit 62.The pebbles then give up their heat in cooling zone 1I and pass downwardto absorb heat from the reaction eiluent passing through conduit 52. Thecooling medium is introduced into cooling zone 1I through conduit 1t or18 and removed therefrom through conduit 18 or 16. This and many othermodifications may be pracd ticed without departing from the scope ofthis invention in either the apparatus shown in Figure 1 or in Figure 2.

Various advantages of the present invention are apparent. Pebble heatersconstructed in the manner described in this application do not have theconventional pebble conveying equipment. The pebbles are transferredaccording to this invention from one zone to another without the usualmechanical conveyor. Other usual mechanical features of pebble heatersare also eliminated, such as star valves, conduits, throats, etc.Furthermore, the pebble heater itself is unitary which enableseconomical construction and opof steam and as a typical example of sucha process the following application will be described. A power unitrequiring approximately 1000 pounds of steam per hour at a temperatureof about 1000 F. utilizes the apparatus of Figure 2 in the lfollowingmanner. Steam is passed through chamber 'H at the rate of a-bout 1000pounds per hour at a pressure of about 20 pounds gage and at an entrancetemperature of about 280 F. The steam in a superheated condition leaveszone 'il through conduit 13 at about 1000 F. A hydrocarbon fuel, such asbutane, is burned in zone 51 with excess air. The flue gas fromcombustion zone 51 passes through a 3 inch diameter conduit 62 at a rateof about 30 feet per second. The pebbles of quartz or sand used for suchoperation preferably have a diameter of about 0.006 of an inch and arereadily suspended in the fluid in conduit 62 and are heatedv above about1500 F. The diameter of conduit 62 is about 3 inches inside diameter andthe diameter of cylinder 53 is about 2 feet. Conduit E2 is about 4 to `6feet in length depending upon the depth of the pebbles accumulating inreaction zone ll.

The apparatus and method for heating gases as described in thisapplication may be used for various other processes than thosespeciiically mentioned. Other chemical reactions to which the presentinvention is applicable comprise dehydrogenation of hydrocarbon, theformation of water-gas from hydrocarbons and steam, the hydrogenation ofcarbon monoxide, depolymerization and dealkylation, etc.

It is to be understood that the form of our invention herewith shown anddescribed is to be taken as preferred example of the same, and thatvarious changes in shape, size and arrangement of parts may be resortedto without departing from the spirit of this invention or the scope ofthe subjoined claims. v

Having described our invention, we claim:

, 1. Apparatus for the treatment of a gas which comprises in combinationan enclosed, hollow body having an outlet at the top thereof and aninlet at the bottom thereof, a iirst perforate septum having a vent forthe passage of gas therethrough positioned across said hollow body andforming an upper chamber in said body, a second imperforate septumhaving a vent for the passage of gas therethrough positioned across saidhollow body so as to form a lower chamber below said second septum andan intermediate chamber between said iirst and second septa, means l forintroducing a gas into said upper chamber,

means for removing gas from said intermediate i chamber, and a conduitpositioned in said intermediate chamber in vertical alignment with saidvents and in close spaced-apart relation to the vent in said secondseptum.

2. Apparatus for the treatment of gas in the presence of pebbles whichcomprises in combination a vertical elongated enclosed vessel having anoutlet at the top thereof and an inlet at the bottom thereof, a rstperforate septum having a vent for the passage of pebbles therethroughpositioned across said vessel so as to form an up-` per chamber therein,a second imperforate sepg tum having a vent for the passage of gastherethrough positioned across said vessel so as to form a lower chamberbelow said second septum and an intermediate chamber between said rstand second septa, means for introducing gasinto said upper chamber,means for removinggas from said intermediate chamber, and conduit meansaligned with said vents and extending upwardly from close proximity tothe vent in said second septum adapted for lifting pebbles by means ofhigh velocity gas to said upper chamber.

which comprises in combination an upright enclosed cylindrical vesselhaving a gas outlet at the top and a iiuid inlet at the bottom thereof,a first perforate septum positioned in said vessel whereby an upperchamber is formed in said body,

Ia second imperforate septum having a central vent for the passage ofgas therethrough positioned in said vessel so as to form a lower chamberbelow said second septum and an intermediate chamber between said firstand second fsepta, an elongated conduit openly communicating betweensaid upper chamber and said intermediate chamber passing through thecenter of said irst septum and extending downward and terminating inclose spaced-apart relation to the vent in said second septum so as toeffect the passage of pebbles from the bottom of said intermediatechamber into and through said conduit to said upper chamber upon thepassage of an upward blast of gas through said vent into said conduit,means for introducing feed gas into said intermediate chamber, and meansfor withdrawing eliluent gas from said intermediate chamber.

4. Apparatus for the treatment of a gas which comprises in combinationan enclosed upright vessel having an outlet at the top thereof and antum and an intermediate chamber between said K rst and second septa, aconduit openly communicating between said upper chamber and saidintermediate chamber passing through said rst septum and extendingdownward and terminating directly over but spaced apart from said ventin said second septum, means for introducing gas into said intermediatechamber, and means for withdrawing gas from said intermediate chamber.

5. Apparatus for the treatment of a gas in the presence of pebbles whichcomprises in combination an enclosed upright vessel having an outlet atthe top thereof and an inlet at the bottom thereof, a first perforateseptum having a central vent positioned in said vessel so as to form anupper chamber therein, a second imperforate septum having a vent for thepassage of gas therethrough positioned in said vessel so as to form 'alower chamber below said second septum and an intermediate chamberbetween said first and second septa, means positioned in said vessel fortransferring pebbles from the lower portion pf said intermediate chamberto said upper chamber comprising a tube element aligned with said ventsin spaced-apart relation to the vent in said second septum, means forintroducing feed gas into said intermediate chambenand means for4withdrawing eiiiuent. gas from said intermediateY chamber.

3. Apparatus for the heat exchange of gases 6. Apparatus for the heatexchange of gases in the presence of pebbles which comprises incombination an upright elongated cylindrical vessel having a gas outletat the top and a gas inlet at the bottom thereof, a rst perforate septumhaving a central vent for the passage of pebbles upwardly therethroughpositioned across the upper portion of said vessel and forming an upperchamber therein, said septum being adapted for uniformly passing pebblesdownwardly over the area thereof while maintaining a multiple layer ofpebbles thereon, a second imperforate funnelshaped septum having acentral vent for the passage of a hot gas therethrough positioned acrosstheY lower portion of said vessel so as to form a lower chamber belowsaid second septum for the combustion of fuel therein andv anintermediate chamber between said first and second septa, means forintroducing' gas tangentially into the lower portion of said upperchamber, means for removing gas from the upper portion of saidintermediate chamber, an elongated open conduit positioned in saidintermediate chamber in alignment with said ventsV and extending fromadjacent the vent in said second septuml only a portion of the length ofsaid intermediate chamber, said conduit havingy a restricted opening inthe lower end thereof and being positioned so as to effect the passageof pebbles from the bottom of said intermediate chamber into and throughsaid conduit and said intermediate chamber to said upper chamber uponpassage of an upward blast of gas through said Vent in said secondseptum into said conduit.

7. The apparatus of claim 6 in which said conduit extends only a minorportion of the length of said intermediate chamber.

8. Apparatus for the heat exchange of gases in the presence of pebbleswhich comprises in combination an upright elongated cylindrical vesselhaving a gas outlet at thetop and a gas inlet at the bottom thereof, afirst perforate septum having a central vent for the passage of pebblesupwardly therethrough positioned across the upper portion of said vesseland forming an upper chamber therein, said septum being adapted foruniformly passing pebbles downwardly over the area thereof whilemaintaining a multiple layer of pebbles thereon1 a second imperforatefunnelshaped septum having a central vent for the passage of a hot gastherethrough positioned across the lower portion of said vessel so as toform a lower chamber below said second septum for the combustion of fueltherein and an intermediate chamber between said first and second septa,means for introducing gas tangentially into the lower portion of saidupper chamber, means for removing gas from the upper portion of saidintermediate chamber, and an elongated open conduit positioned in saidintermediate chamber in alignment with said vents and extending fromadjacentv the vent in said second septum only a portion of the length ofsaid intermediate chamber, said conduit having a restricted opening inthe lower end thereof and positioned so as to effect the passage ofpebbles from the bottom of said. intermediate chamber into and throughsaid conduit and said intermediate chamber to said upper chamber uponthe passage of an upward blast of gas through said vent in said secondseptum into said conduit.

9. Apparatus for the. heat exchange of fluids in the presence of pebbleswhich comprises. in combination an upright closed cylindrical vesselhaving a gas outlet' at the top and a gas inlet at the bottom, a firstperforate septum positioned in the upper portion of said vessel formingan upper chamber therein and adapted for gradually passing pebblestherethrough over the entire crosssection of said vessel whilemaintaining a substantial layer of pebbles thereon, a second funnelshaped imperforate septum having a vent in the center for the passage ofgas therethrough and positioned in the lower portion of said vessel soas to form a lower chamber below said second septum for the combustionof fuel therein and an intermediate chamber between said rst and secondsepta, an elongated conduit extending from the lower portion of saidupper chamber through said rst septum and terminating in saidintermediate chamber directly above and Iadjacent said vent so as toeffect the passage of pebbles from the bottom of said intermediatechamber into and through said conduit to said upper chamber upon thepassage of an upward blast of gas through said vent into said conduit,means for introducing feed gas into the upper portion of saidintermediate chamber, means for withdrawing efrluent gas from the lowerportion of said intermediate chamber, and means for preventing thepassage of pebbles through said outc and positioned in the lower portionof said vessel so as to form a lower chamber below said second septumfor the combustion of fuel therein and an intermediate chamber betweensaid first and second septa, an elongated conduit extending from thelower portion of said upper chamber through said rst septum andterminating in said intermediate chamber directly above and adjacentsaid Vent so as to effect the passage of pebbles from the bottom of saidintermediate chamber into and through said conduit to said upper chamberupon the passage of an upward blast of gas through said vent into saidconduit, means for introducing feed gas into said intermediate chamber,and means for withdrawing an effluent from said intermediate chamber.

11. A method of heating a gas by direct contact with hot pebbles whichcomprises burning a combustible mixture, passing a blast of theresulting gaseous mixture through an orice into the lower end of anarrow elongated Vertical confined zone directly above said orifice soas to heat and entrain pebbles from the area surrounding said orificeand the lower end of said zone, thereby lifting the resulting hotpebbles through said zone into an upper expanded zone; passing a gasthrough said upper zone in direct heat exchange with said pebbles;maintaining a compact layer of pebbles in the lower portion of saidupper zone while simultaneously passing pebbles by gravity through aplurality of paths distributed over the bottom of said upper zone to asubjacent zone y surrounding said narrow verticalv confined zone,thereby passing freely falling pebbles over substantially the entirehorizontal cross section o1 said subjacent zone to a bed of samesurrounding end of a narrow elongated vertical confined zone directlyabove said orifice so as to heat and entrain pebbles from the areasurrounding said orifice and the lower end of said zone, thereby liftingthe resulting hot pebbles through said zone into an upper expandedheating zone; contacting said hot pebbles in said upper zone with a gasto be heated thereby heating said gas; withdrawing and collecting aneiiiuent from said upper zone; maintaining a compact layer of pebbles inthe lower portion of said upper zone while simultaneously passingpebbles by gravity through a pluralityof paths distributed over thebottom of said upper zone to a subjacent zone surrounding said narrowvertical confined zone, thereby passing freely falling pebbles oversubstantially the entire horizontal cross section of said subjacent zoneto a bed of same surrounding said lower end of said narrow zone; andwithdrawing gaseous mixture from said subjacent zone.

13. A method of heating gas by direct contact with hot pebbles whichcomprises burning a combustible mixture; passing a blastl of theresulting gaseous mixture through an orifice into the lower end of anarrow elongated vertical conned zone spaced apart vertically from saidorifice and extending to an expanded upper zone, thereby entrainingpebbles from the area surrounding said orifice and the lower end of saidzone and simultaneously heating and lifting the resulting hot pebblesthrough said zone into said upper expanded zone; withdrawing gaseousmixture from said upper zone; maintaining a compact layer of pebbles inthe lower portion of said upper zone while simultaneously passingpebbles from said layer by gravity through a plurality of pathsdistributed over the bottom of said upper zone to a subjacent zonesurrounding said narrow vertical confined zone, thereby passing freelyfalling pebbles over substantially the entire horizontal cross sectionof said subjacent zone to a bed of same surrounding said lower end ofsaid narrow zone; introducing feed gas to said subjacent zone in directheat exchange with said freely falling pebbles and withdrawing andcollecting an eiuent from said subjacent zone.

14. A method for conversion of hydrocarbons which comprises passing ablast of hot combustion gas through an orifice into the lower end of anarrow vertical elongated Aconfined zone directly over said orifice soas to heat and entrain pebbles from the area surrounding said orice andthe lower end of said zone, thereby ejecting the resulting hot pebblesthrough said zone into an upper expanded conversion zone while retainingsaid combustion gas in a subjacent zone surrounding said narrow zone;contacting the hot pebbles in said conversion zone with hydrocarbon gasso as to heat and convert the same to desirable product; withdrawing andrecovering an eiuent from said conversion zone; maintaining a compactlayer of pebbles in the bottom of said conversion zone whilesimultaneously passing pebbles to said subjacent zone by gravity througha plurality of paths distributed over the bottom of said conversionzone, thereby passing freely falling ypebbles through said subjacentzone in direct heat exchange with said combustion gas to a bed of samesurrounding said lower end of said narrow zone for reheating andrecirculating to the conversion zone; and withdrawing combustion gasfrom said subjacent zone.

15. A method for conversion of hydrocarbons 'which comprises passing ablast of gas comprising hydrocarbon through an orifice into the lowerend of a narrow vertical elongated confined zone spaced apart verticallyfrom said orifice so as to `entrain pebbles from the area surroundingsaid orifice and the lower end of said zone, thereby ejecting thepebbles through said zone into an upper expanded pebble heating zonewhile retain ing said hydrocarbon gas in a subjacent conversion zonesurrounding said narrow zone; contacting the pebbles in said pebbleheating zone with i hot combustion gas so as to heat said pebbles-- to atemperature above a predetermined conversion temperature; withdrawingcombustion gas .from said pebble heating zone; maintaining a heatingzone to said subjacent conversion zone;

gravitating said pebbles through said subjacent conversion zone incontact with the hydrocarbon y gas therein, thereby heating andconverting said hydrocarbon and simultaneously returning said pebbles toa bed of same surrounding said lower end of said narrow zone forrecirculating to the pebble heating zone; and withdrawing and col--lecting an eiuent from said subjacent conversionA zone.

16, A method for conversion of hydrocarbons which comprises passing ablast of hot combustion gas through an orifice into the lower end of anarrow elongated conned zone directly over i said orifice so as to heatand entrain pebbles from the area surrounding said orifice and the lowerend of said zone, thereby ejecting the resulting hot pebbles throughsaid zone into an upper expanded separation zone; withdrawing combustiongas from said upper zone; collecting hot pebbles in the bottom of saidupper zone and passing the same by gravity through a plurality of pathsdistributed over the bottom of said upper zone to a subjacent conversionzone surrounding said narrow vertical zone, thereby passing freelyfalling pebbles through said conversion zone to a bed of samesurrounding said lower end of said narrow zone for reheating andrecrculating to said upper separation zone; introducing hydrocarbonv gasinto said conversion zone into Contact with the gravitating hot pebblestherein so as to effect conversion thereof; and withdrawing a conversioneiiluent from said conversion zone.

17. Apparatus for the treatment of a gas in the presence of pebbleswhich comprises in combination an upright, elongated, cylindrical vesselhaving a gas outlet in the top section and an orifice in the bottomthereof; a perforate septum having a central vent of larger size thanthe other perforations in said septum, said septum being positionedacross the upper portion of said vessel so as to form an upper and alower chamber therein and being adapted for gradually passing pebblesdownwardly therethrough uniformly over the horizontal cross section ofsaid vessel except at said vent; a plurality of conduits opening intosaid lower chamber through the cylindrical walls of said vessel forintroducing to and withdrawing gas from said lower chamber; and anelongated open ended conduit of relatively small crosssectional areaextending between said vent and said ori'lce in. close spaced-apartrelation at its lower end to saidk oriiice so as to provide a passagewayfor said pebbles to flow into the end of said conduit from thesurrounding space and adapted so as to effect the passage of pebblesfrom the bottom of said lower chamber into and through said conduit intosaid upper chamber upon the passage of an. upward blast of gas throughsaid oriiice.

18.. Apparatus for the treatment of uid in the presence of heat-exchangepebbles which comprises in. combination an upright elongated cylindricalvessel having a gas outlet in the upper portion and gas inlet oriiice inthe bottom thereof, said bottom being cupped to cause flow of saidpebbles toward said oriiice; a transverse perforate septum in saidvessel intermediate the ends thereof dividing said vessel into an uppercham- `ber and a lower chamber extending from said septum to the lowerend of said vessel, the perforations in said septum providing pebblepassageways from said upper to said lower chamber; a vent in said septumlarger than said perforations providing a passageway for pebblesupwardly therethrough; a gas inlet in said upper chamber; a gas outletin said lower chamber; and an elongated conduit of relatively smallcrosssection open at both ends and fixed in said lower chamber inalignment with said oriiice and said vent, its lower end approaching theupper end of said orifice in spaced-apart relation thereto so that ablast of gas injected upwardly through said orice entrains and liftspebbles from the lower end-of said lower chamber to said upper chamber.

19. Apparatus for the treatment of a Iiuid in contact with pebbles,which comprises in combination an upright, elongated cylindrical vesselhaving a gas outlet at the vtop and an oriiice in 16y the bottomthereof; a perforated septum having a central vent larger than the otherperforations in said septum for the passage of pebbles upwardlytherethrough, said septum being positioned across the upward portion ofsaid vessel and forming an upper and lower chamber therein and beingadapted for gradually passing pebbles downwardly therethrough uniformlyover the horizontal cross-section of said vessel except at said ventwhile maintaining multiple layers of pebbles thereon; means forintroducing gas into said upper chamber; means for removing gas fromsaid lower chamber; and an elongated openended conduit of relativelysmall cross-sectional area positioned in. said lower chamber inalignment with said vent and said oriiice extending therebetween inclose spaced-apart relation at its lower end to said orice so as toprovide a passageway for said pebbles to flow into the end of saidconduit from the surrounding space, and adapted so as to effect thepassage of pebbles from the bottom of said lower chamber into andthrough said conduit into said upper chamber upon the passage of anupward blast of gas through said oriiice.

CRUZAN ALEXANDER.

HARRIS A. DUTCHER.

REFERENCES CITED The following references are of record in the iile ofthis patent:

UNITED STATES PATENTS Number Name Date 2,405,395 Bahlke et al Aug. 6,1946 2,412,152 Huff Dec. 3, 1946 2,425,098 Kassel Aug. 5, 1947 2,457,232Hengstebeck Dec. 28, 1948

11. A METHOD OF HEATING A GAS BY DIRECT CONTACT WITH HOT PEBBLES WHICHCOMPRISES BURNING A COMBUSTIBLE MIXTURE, PASSING A BLAST OF THERESULTING GASEOUS MIXTURE THROUGH AN ORIFICE INTO THE LOWER END OF ANARROW ELONGATED VERTICAL CONFINED ZONE DIRECTLY ABOVE SAID ORIFICE SOAS TO HEAT AND ENTRAIN PEBBLES FROM THE AREA SURROUNDING SAID ORIFICEAND THE LOWER END OF SAID ZONE, THEREBY LIFTING THE RESULTING HOTPEBBLES THROUGH SAID ZONE INTO AN UPPER EXPANDED ZONE; PASSING A GASTHROUGH SAID UPPER ZONE IN DIRECT HEAT EXCHANGE WITH SAID PEBBLES;MAINTAINING A COMPACT LAYER OF PEBBLES IN THE LOWER PORTION OF SAIDUPPER ZONE WHILE SIMULTANEOUSLY PASSING PEBBLES BY GRAVITY THROUGH APLURALITY OF PATHS DISTRIBUTED OVER THE BOTTOM OF SAID UPPER ZONE TO ASUBJACENT ZONE SURROUNDING SAID NARROW VETICAL CONFINED ZONE, THEREBYPASSING FREELY FALLING PEBBLES OVER SUBSTANTIALLY THE ENTIRE HORIZONTALCROSS SECTION OF SAID SUBJACENT ZONE TO A BED OF SAME SURROUNDING SAIDLOWER END OF SAID NARROW ZONE; AND PASSING A GAS THROUGH SAID SUBJACENTZONE IN DIRECT HEAT EXCHANGE WITH SAID FREELY FALLING PEBBLES.